In eukaryotes, all biological functions, including DNA replication, cell cycle progression, energy metabolism, and cell growth and differentiation, are regulated through the reversible phosphorylation of proteins. The phosphorylation state of a protein determines not only its function, subcellular distribution, and stability, but also what other proteins or cellular components it associates with. The balance of specific phosphorylation in the proteome as a whole, as well as of individual members in a biochemical pathway, is thus used by organisms as a strategy to maintain homeostasis in response to an ever-changing environment. The enzymes that carry out these phosphorylation and dephosphorylation steps are protein kinases and phosphatases, respectively.
The eukaryotic protein kinase family is one of the largest in the human genome, comprising some 500 genes [1,2]. The majority of kinases contain a 250-300 amino acid residue catalytic domain with a conserved core structure. This domain comprises a binding pocket for ATP (less frequently GTP), whose terminal phosphate group the kinase transfers covalently to its macromolecular substrates. The phosphate donor is always bound as a complex with a divalent ion (usually Mg2+ or Mn2+). Another important function of the catalytic domain is the binding and orientation for phosphotransfer of the macromolecular substrate. The catalytic domains present in most kinases are more or less homologous.
A wide variety of molecules capable of inhibiting protein kinase function through antagonising ATP binding are known in the art [3-7]. By way of example, the applicant has previously disclosed 2-anilino-4-heteroaryl-pyrimidine compounds with kinase inhibitory properties, particularly against cyclin-dependent kinases (CDKs) [8-12]. CDKs are serine/threonine protein kinases that associate with various cyclin subunits. These complexes are important for the regulation of eukaryotic cell cycle progression, but also for the regulation of transcription [13,14].
The present invention seeks to provide new so-called “constrained” heteroaryl-substituted pyrimidine derivatives, in which free rotation of the heteroaryl substituent is hindered. More specifically, the invention relates to 4,5-dihydro-thiazolo-, oxazolo-, and imidazolo-[4,5-h]quinazolin-8-ylamines that have broad therapeutic applications in the treatment of a number of different diseases and/or that are capable of inhibiting one or more protein kinases.